Pattern-controlled machine tools



Nov. 3, 1959 v F. R. M. CLARKE ETAL 2,9 82

PATTERN-CONTROLLED MACHINE TOOLS Filed March 16, 1956 4 Sheets-Sheet 1 Nov. 3, 1959 F. R. M. CLARKE ETAI- 2,911,132

PATTERN-CONTROLLED MACHINE TOOLS Filed March 16, 1956 4 Sheets-Sheet 2 lzz m Nov. 3, 1959 F. R. M. CLARKE ETAL 2,911,182

PATTERN-CONTROLLED MACHINE TOOLS Filed March 16, 1956 4 Sheets-Sheet 3 lzzvewmpa Nov. 3, 1959 F. R. M. CLARKE ETAL 2,911,182

PATTERN-CONTROLLED MACHINE TOOLS 4 Sheets-Sheet 4 Filed March 16, 1956 IJZU elztbl FJiM. C lamlce United States Patent O PATTERN-CONTROLLED MACHINE TOOLS Frederick Robert Milroy Clarke, London, and Hermann Patented Nov. 3, 1959 ice freedom relatively to the valve member 3 and by reason of the fact that it is carried by the said member it also has lateral freedomof movement. Both of these movements are small and are usually of the order of about 0.002 inch. To minimise frictional resistance to axial V movement of the spindle 7 it is preferably made of smaller Franz Plant, New Malden, England, assignors to Precision Grinding Limited, Mitcham Junction, Surrey, England Application March '16, 1956, Serial No. 572,110

4 Claims. (Cl. 251-3) This invention relates to hydraulically operated machine tools of the kind in which the relative movements of a tool and work-piece are controlled by contact of a tracer with a pattern to be reproduced.

The object of the invention is to provide improved means responsive to the interaction of the tracer and pattern for controlling the hydraulically operated parts.

The essential feature of the invention consists of a tracer head which comprises the combination of a tracer spindle having axial and lateral freedom of movement, a valve member which carries and is movable by the spindle and has only lateral freedom of movement, and a valve member having axial freedom of movement mounted coaxially with and movable by axial or lateral movements of the spindle.

The invention also comprises a hydraulic system under the control of the tracer head as hereinafter described.

In the accompanying drawings: Figure 1 is a sectional front elevation, Figure 2 a side elevation and Figure 3 a plan of a tracer head embodying the invention and adapted for use more particularly on a milling machine. Figure 4 is a cross section on the line a-a, and Figure 5 is a cross section on the line bb of Figure 1.

Figures 6 and 7 are respectively a front elevation and a sectional side elevation of a milling machine provided with the invention, and Figure 8 is a sectional side elevation illustrating control valves for a slide actuating means in the said machine. Referring to Figures 1 to 5 the tracer head there shown comprises a substantially cylindrical housing 1 having a central vertical bore. The housing is composed of a substantially cylindrical main part In, and annular plates 15, 15a and 15b arranged coaxially with the main part, and secured to the lower end thereof by screws 150. The annular plate 15a and the adjacent faces of the annular plates 15 and 15b form within the lower part of the housing a shallow cylindrical chamber 2 which is coaxial with, and of larger diameter than, the central bore in the housing, and which contains a valve member 3 in the form of a circular plate having parts of its upper and lower faces in close contact with the corresponding faces of the plates 15 and 15b. From each face of the valve member 3 extends a hollow boss which may be formed integrally with the member 3, but more conveniently these bosses are formed by a bush 4 inserted tightly through a central bore in the said member. The diameter of the valve member is sufiiciently smaller than that of the containing chamber to permit its required lateral freedom.

The tracer 5 is secured to a holder 6 formed on or secured to a spindle 7 which extends through the bush 4, the said holder 6 being secured to a flexible sealing diaphragm 8 attached to the housing 1. On the inner end of the spindle 7 is formed or secured a collar 9 which is supported on the adjacent end of the bush 4, and between this collar and an annular shoulder on the bush is mounted a spring 10 which serves to counterbalance the'weight of the tracer spindle. The spindle 7 has axial diameter than the bore of the bush, and is supported laterally in the bush by bearing balls 11.

High pressure liquid is conveyed to the annular space around the valve member 3 by a passage 12 in the housing, which passage receives the liquid from another passage 13 which leads to a piston valve to be hereinafter described, and the purpose of the valve member 3 is to control the flow of liquid from the said annular space to each of four equi-spaced delivery passages 14 in the housing, the outlet ends of the latter passages at the upper end of the housing being adapted for connection thereto of flexible pipes for leading the liquid to the hydraulic slide controlling means to be hereinafter described.

To enable the control of the liquid from the said annular space to be sensitive to small movements of the valve member 3, the outlet ports from the said chamber are preferably made in the form of narrow arcuate slits, and a'convenient mode of construction is shown in Figures 1 and 5. In the annular plate 15 is formed a circular recess in which is placed another circular plate 16. In the plate 15 are formed ports 17 situated opposite the ends of the passages 14, and from these ports 17 extend lateral ports 18 which are situated opposite notches 19 formed in the periphery of the inner plate 16. Each such notch has formed in it a sloping surface as shown in Figure 1, which at its lower edge forms with'the inner periphery of the recess in the plate 15 a narrow arcuate port 20 as shown in Figure 5. The arrangement is such that .when in its central position the valve member 3 closes all the ports 20, and a small lateral movement in any direction suflices to open at least one of the ports 20 to a corresponding extent.

In the upper part of the housing is contained a vertically slidable valve member 21 of the piston type, for controlling the flow of high pressure liquid required for actuating a vertically movable slide as hereinafter described. This member is contained in a ported bush 22 in the housing, and in the housing are formed annular recesses 23, 24, 25 which are respectively connected to the" liquid inlet passage 13 above mentioned, a passage 26 through which the liquid is conducted to the slide to be actuated, and a passage 27 by which the liquid is returned to a sump on the inlet side of the liquid supply pump. The valve member 21 is provided with a single circumferential land 28 which controls the ports associated with the recess 24. This land may in one position of the valve close these ports,--but preferably it is made rather narrower than these ports so that a continuous but restricted flow can occur between the passages 13 and 27 when the said member is in its central position, When moved upwardly from the position shown it increases the rate of flow between the passages 13 and 26 and restricts or interrupts the flow to the passage 27. Between the lower end of the valve member 21 and the upper end of the tracer spindle 7 there is arranged a thrust piece 29. This extends through a hollow boss 30 formed on the above mentioned plate 15, and in this boss is contained a liner 31 which carries bearing balls 32 by which the thrust piece is laterally supported. The lower end of the member 21 is held in contact with the upp-.r end of the thrust piece by a spring 33 acting and the tracer spindle 7 is formed a conical or other suitably shaped recess for containing a ball 36.

When a vertical movement is given to the tracer spindle the ball transmits this movement through the thrust piece to the valve member 21. Also when a lateral movement is given to the tracer spindle and valve member 3 a vertical movement is given to the valve member 21 by the lateral interaction of the conical recess in the tracer spindle and the ball. serves to return the tracer spindle and the valve member 3 to the central position under the pressure exerted by the spring 33.

The mode of controlling a milling machine by the tracer head above described will now be described with reference to Figures 6-8. The machine shown by Figtires 6 and 7 includes a pair of vertically adjustable tables 38, 39 on which can be respectively secured the workpiece and the pattern. The rotary cutting tool 40 is carried by a spindle 41 which is mounted on a vertically movable slide 42 on the forward end of a horizontally reciprocable slide 43 which also carries an electric motor 44 for rotating the tool, motion being transmitted from the motor to the tool by pulleys and belts as shown or in any other convenient manner. On the forward end of the slide 43 is secured a fixed vertical ram 45 which is contained in a cylinder 46 formed in the vertical slide 42. The tracer head 1 is secured to the slide 42 by an arm 47. High pressure liquid is conveyed from the tracer head to the cylinder 46 by a pipe (not shown) contained in the arm 47.

Actuation of the slide 43 is effected by low pressure liquid admitted to a cylinder 48 which is secured to a traversing slide 49 on which the slide 43 is mounted, the traversing slide (which moves at right angles to the slide 43) being mounted on the pedestal of the machine. In the said cylinder 48 is contained a piston 50 secured to a rod 51 which extends through the ends of the cylinder and is secured to the slide 43 (Figure 7). The traversing slide 49 is actuated in like manner by a like mechanism comprising a cylinder 52 secured to the slide and a piston 53 secured to the pedestal.

In conjunction with each of the cylinders 48, 52, there are provided a pair of control valves, and a description will now be given of the valves of the cylinder 48 associated with the reciprocatory slide 43 which carries the slide 42, these valves and the cylinder being shown in Figure 8. Each valve comprises a hollow body part 54 having therein a cylindrical chamber which contains a piston valve member 55 loaded by a spring 56 which tends to move the said member to its open position. High pressure liquid is admitted to one end of one of the valves by a pipe 57 connected to one of the outflow passages 14 of the tracer head, and the other valve is connected by a similar pipe 57 to the diametrically opposite passage 14 in the tracer head. This liquid opposes the action of the spring 56 and is partially counterbalanced by the low pressure liquid which is conveyed by a passage 58 to the end of the valve adjacent to the spring. The high pressure liquid from the tracer head is allowed to flow at a regulated rate from the valve to a sump or the inlet side of the liquid supply pump by way of a restricted passage 59 which is controlled by an adjustable throttle 60. The extent of movement of the valve member 55 in the direction in which it is movable by the spring is restricted by an adjustable stop 61. One of the valve body parts is connected to one endof the cylinder 43 by a pipe 62, and the other end of the cylinder is connected to the oher valve body The ball 36 further part by a pipe 63. Slide actuating liquid is conveyed to cylinder 48. Control of the liquid supplied to one or the other of the two valves above described is effected by a manually or mechanically operable reversing and stop valve (not shown). Assuming the motive liquid is entering the left hand valve shown in Figure 8, this liquid can flow along the pipe 62 to one end of the cylinder '48, causing the piston 50 to move to the left and liquid displaced from the cylinder passes along the pipe 63 to the right-hand valve and thence to a sump or the inlet side of the pump. So long as the valve member 3 in the tracer head occupies its central position, the motive liquid flows through both of the control valves and the cylinder until the movement of the slide is completed, and then by the action of a tappet or other means actuated by the slide the reversing valve is actuated for reversing the direction of flow and consequently reversing the direction of the slide. If, however, during either of these movements a small movement is given to the valve member 3 by the tracer 5, causing a restricted flow of high pressure liquid from the tracer head through either of the pipes 57 to one of the valves 55, the latter will be moved for restricting or interrupting the flow of low pressure liquid from the cylinder 48. A still further movement of the valve member 3 in the tracer head will enable f'ull flow of high pressure liquid to act on the valve, so causing it to move to the position in which it allows high pressure liquid to pass to the end of the cylinder connected to the valve, and the high pressure liquid will then override the action of the low pressure liquid in the other end of the cylinder and so cause a reverse motion to be given to the slide.

The action of the motive liquid in the traversing cylinder 52 is controlled in like manner by another pair of valves similar to those shown in Figure 8 and connected by pipes to the other pair of passages 14 in the tracer head.

In general the mode of action of the machine above described is as follows:

Assuming that, in the simplest case, the pattern has a plain flat horizontal surface over which the tracer 5 is caused to move in contact with the said surface, no vertical or lateral movement of the tracer will occur, and the slide 43 carrying the tool and tracer will be reciprocated at a uniform rate under control of the valves shown in Figure 8. At the same time the traversing slide 49 is moved continuously at a slOW rate until the tracer has passed over the whole of the surface of the pattern.

Assuming, however, that the pattern has on any portion of its surface, a gradually sloping part which can impart a simple vertical movement to the tracer 5, in an upward direction, the effect of this isto cause high pressure liquid to flow through the piston valve of the tracer head to the cylinder 46 of the tool slide, so causing the tool slide to move upwardly to a corresponding extent. So long as the said sloping part of the pattern offers insuflicient lateral resistance to the tracer 5 to effect a lateral movement of the tracer, only the piston valve in the tracer head will be actuated. But if an abrupt change of shape in the surface of the pattern is encountered by the tracer 5, it will move laterally and so actuate the valve member 3, thereby causing high-pressure liquid to pass through the tracer head to the controlling valves of the cylinder 48 for arresting the motion of the slide or reversing its direction. At the same time the lateral movement of the valve member 3 will (through the ball 36) cause the piston valve member 21 to be moved upwardly with concurrent upward movement of the slide 46 carrying the tool and tracer head. If the change of the form of the surface of the pattern is such as to cause the tracer so to move the valve member 3 as to expose a passage 14 leading to the control valves of the cylinder 52 of the traversing slide 53, the motion of this slide also will be modified in like manner.

In the foregoing, the invention has been described as applied to .a milling machine, but the invention is not tools, such as lathes.

5 I restricted to this particular use, as it may be applied in essentially the same mannertoother copying machine 'Having thus described our invention what we claim as new and desire to secure by Letters Patent is:

1. A tracer head for a hydraulically operated machine tool of the kind specified, comprising in combination'a housing having therein a central bore and a cylindrical valve chamber coaxial with and of larger diameter than the bore, a centrally bored first valve member mounted with freedom of movement in the valve chamber and having a pair of opposite faces in close slidable contact with corresponding end faces of the valve chamber for confining the freedom of the valve member to lateral movement thereof relative to the central bore of the housing, an axially and laterally movable tracer spindle extending through and slidably mounted in the central bore of the first valve member so that the tracer spindle is incapable of tiltingmovement, but can serve to impart lateral movement to thevalve'member, ports controllable by the first valve member,,a second valve member of the piston type mounted within the central 'borein the hous? ing, additional ports controllable by the second valve member, and means for imparting axialmovements to the second valve member in response to lateral movements as 'well as axial movements of the tracer spindle.

2. A tracer head according to claim 1, in which the means for imparting axial movementsto the second valve member comprise in combination a thrust piece in the rated in the housing and having therein a circular recess inswhich the first mentioned plate is located, the said notches extending to said one side of said circular plate to form with the periphery of the said recess narrow arcuate openings arranged to communicate with the valve chamber under the control of the first valve member.

4. A tracer head according to claim 1, and having a bush inserted tightly through the centrally bored first valve member, and serving as a medium through which the first valve member serves to support the tracer spindle.

References Cited in the file of this patent UNITED STATES PATENTS 2,682,202 Roehm June 29, 1954 2,745,624 Turchan May 15, 1956 2,749,810 Turchan June 12, 1956 2,766,003 Dall et al. Oct. 9, 1956 2,787,437 Turchan Apr. 2, 1957 

